Coulombic Attraction
Definition and meaning of Coulombic Attraction in chemistry.
Coulombic attraction is the electrostatic pulling force between oppositely charged particles, such as a cation and an anion, described quantitatively by Coulomb's law. It arises because opposite charges lower the system's potential energy as they approach one another.
In more detail
The force follows F = k(q1q2)/r², so attraction strengthens rapidly as charge magnitudes increase or the distance between particles decreases. This same interaction underlies ionic bonding, holding cations and anions together in a crystal lattice, and contributes to attractions between the nucleus and electrons in an atom. Because the force depends on charge and distance, lattice energy and melting points of ionic compounds generally rise with higher ionic charge and smaller ionic radii.
Key facts
| Governing equation | F = k(q1q2)/r² (Coulomb's law) |
|---|---|
| Constant k | 8.99 × 10⁹ N·m²/C² |
| Nature of force | Attractive between opposite charges; repulsive between like charges |
| Field | Physical Chemistry |
In sodium chloride (NaCl), the coulombic attraction between Na⁺ cations and Cl⁻ anions holds the ions in a rigid, alternating crystal lattice, giving the solid its high melting point of 801°C.
Frequently asked questions
Is coulombic attraction the same as an ionic bond?
Coulombic attraction is the underlying electrostatic force; an ionic bond is the chemical bond that results from strong, net coulombic attraction between oppositely charged ions in a compound.
Does coulombic attraction depend on distance?
Yes, it is inversely proportional to the square of the distance between charges, so it weakens quickly as ions move apart and strengthens sharply as they get closer.